#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

void main(int argc, char *argv[]) {
  if (argc < 2) {
    fprintf(stderr, "usage: %s <program> [args...]\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  printf("parent process PID=%d is starting\n", getpid());

  pid_t pid = vfork(); // use vfork to create child process

  if (pid < 0) {
    // vfork fail
    perror("vfork fail");
    exit(EXIT_FAILURE);
  } else if (pid == 0) {
    // child process
    printf("child process PID=%d will start: %s\n", getpid(), argv[1]);

    // execute program which is pass in via argv
    execvp(argv[1], &argv[1]);

    perror("execvp fail");
    exit(EXIT_FAILURE);
  } else {
    // parent process
    printf("parent process PID=%d wait for child process PID=%d\n", getpid(), pid);

    int status;
    pid_t wait_pid = waitpid(pid, &status, 0); // wait for child process terminating

    if (wait_pid < 0) {
      perror("waitpid fail");
    } else if (WIFEXITED(status)) {
      printf("child process exit，exit code: %d\n", WEXITSTATUS(status));
    } else if (WIFSIGNALED(status)) {
      printf("child process is terminated by signal，signal is: %d\n", WTERMSIG(status));
    }

    printf("parent process exit\n");
  }

  exit(0);
}